Input devices, such as microphones or other devices providing an analog signal sensitive to introduced noise, being connected by wire and relying on an applied bias voltage may face electromagnetic compatibility problems due to loops being formed e.g. by multiple grounding points. In the case of microphones, high currents to other parts of a device may give rise to voltage fluctuations, which can be discovered in the microphone signal as for example low frequency noise, often called “bumble bee” sound. Other problems that may arise in wired connections using a common reference for input and output devices can be echo effects. These effects normally have to be dealt with by well-balanced designs of how wires and components are positioned and circuitry and signal processing for attenuating known noise. WO 02/056511 discloses an approach for dealing with such noise by enabling generation of a replica of periodic interference that is disturbing a desired signal so as to subtract out an estimation of the periodic interference from the infected signal. The signal is bandpass filtered around an expected frequency of the interfering component, and a fundamental frequency thereof may thereafter be ascertained. Harmonics of the fundamental frequency are generated so as to reconstruct an estimate of the interfering component in the frequency domain using determined weights and Fourier series theory. The interfering component estimate is subtracted to form the received signal to determine a desired component estimate. The weights may be optionally adjusted in a feedback loop.
However, there is also a desire to avoid that these interfering effects occur, or at least alleviate occurrence of them.